SCM435 identifies a chromium–molybdenum steel
SCM435 is widely encountered in fasteners, machinery and cold-forming applications. Its full designation identifies a grade in the JIS G 4053 structural alloy-steel system. This article checks the classification and composition examples against JIS G 4053:2008; it does not declare that edition to be the latest or replace the edition specified by the customer.
Read SCM in its own standard context
SCM identifies the chromium–molybdenum alloy-steel series. Steel, chromium and molybdenum provide a useful mnemonic for S, C and M in this context. That mnemonic is not a universal decoding rule for every Japanese steel designation.
JIS G 4053 groups SCM435 among chromium–molybdenum steels for machine structural use. Its classification is distinct from stainless, tool, spring and bearing steel families.
435 is a grade identifier, not a literal percentage
The complete numeric part 435 must not be read as 0.435% carbon. Table 2 of the reviewed edition specifies the carbon range for SCM435 as 0.33–0.38% by mass. The grade number is associated with a composition range; the number alone is not an acceptance result.
| Grade | Specified C range, mass % |
|---|---|
| SCM415 | 0.13–0.18 |
| SCM420 | 0.18–0.23 |
| SCM425 | 0.23–0.28 |
| SCM430 | 0.28–0.33 |
| SCM435 | 0.33–0.38 |
| SCM440 | 0.38–0.43 |
| SCM445 | 0.43–0.48 |
These are selected carbon limits, not a complete chemical specification. SCM410 is not included in this illustrative list because it is not listed in Table 1 of the edition checked here.
Why not shorten it to SCM35?
Use the complete symbol required by the applicable standard. SCM435 cannot simply be renamed SCM35, and the three digits should not be converted into an unverified carbon percentage. Read the identifier together with the standard’s composition table and delivery requirements.
Comparative grades are not automatic substitutes
SCM435 is often discussed alongside 35CrMo, 34CrMo4 and SAE/AISI 4135 or 4137. These names belong to different standard systems. A comparison does not establish identical composition limits, permissible analysis deviations, product requirements or interchangeability. Supply and acceptance must follow the specified grade, product standard, edition and technical agreement.
Application performance requires the right condition
Appropriate processing and heat treatment can provide useful strength, hardenability and toughness for automotive bolts, machinery fasteners, shafts, gears, pins and other load-bearing parts. The grade name alone does not guarantee those properties in any supplied wire condition.
- Confirm the steel grade, standard edition and product form.
- Specify delivery condition, drawing and annealing requirements.
- Evaluate steel cleanliness, inclusions, microstructure, surface condition and decarburization.
- Validate cold-heading deformation, lubrication, dies and equipment.
- Confirm the final heat-treatment route and required component properties.
A professional reading of SCM435 therefore combines the chromium–molybdenum grade family, the specified chemistry and the verified manufacturing route. It is more useful than treating a similar grade name as a substitution approval.